1. Field of the Invention
The present invention relates to a fuel supplying system of LPI (liquefied petroleum injected) engine, and more particularly to a fuel supplying system of LPI engine that is capable of improving performance of a fuel pump by decreasing suction pressure thereof.
2. Description of Related Art
An LPI engine includes an LPI fuel pump feed therein so as to realize stability of fuel supplying performance when forcedly feeding fuel thereto.
That is, the fuel pump is mounted inside a fuel tank, and liquid-state LPG (liquefied petroleum gas) fuel that is forcedly fed is injected by an injector.
The LPI engine is suitable for corresponding to strict emission regulations, and can improve engine starting in winter while inducing emission output reduction of the engine.
As shown in FIG. 3, a conventional fuel supplying system of LPI engine includes a fuel pump 21 mounted inside a sub-fuel tank 20 in a fuel supplying line 30 in order to feed fuel stored inside a main fuel tank 10 to the engine, and then the fuel supplied from the fuel pump 21 is injected by an injector (not shown) to a combustion chamber through the fuel supplying line 30. Unused fuel is returned through a fuel return line 40.
Herein, safety valves 50 are respectively mounted between the main fuel tank 10 and the fuel pump 21, between the fuel pump 21 and the engine in the fuel supplying line 30, and between the fuel pump 21 and the fuel tank 10 in the fuel return line 40.
The conventional fuel supplying system of an LPI engine must follow regulations on LPG vehicles.
The regulations state that an electrical cut-off valve, an overflow prevention valve, a manual cut-off valve, etc., are to be mounted at an exit of the main fuel tank 10.
That means that the main fuel tank 10 should be closed and sealed by closing the electrical cut-off valve in case of failure of starting of the engine.
Further, a safety valve should be provided so as to prevent leakage of fuel of the fuel supplying line 30 in the main fuel tank 10 in the case of a vehicle accident.
At this time, fuel should flow into the fuel pump 21 from the main fuel tank 10 without air intake.
Therefore, the safety valves should be mounted at the fuel supplying line 30 and the fuel return line 40 connecting the main fuel tank 10 and the sub-fuel tank 20, and thereby the system is complicated and manufacturing cost is increased due to duplication of the safety valves 50.
In addition, after suction back pressure generated by the fuel pump 21 is reduced by a volume of the sub-fuel tank 20, the pressure is transmitted to the main fuel tank 10, and thereby fuel intake performance is deteriorated.
Herein, because pressure of the interior of the main fuel tank 10 is high, particularly in summer, fuel intake performance is superior.
However, in winter, because pressure of the interior of the main fuel tank 10 is similar to atmospheric pressure, fuel intake performance depending on the performance of the fuel pump 21 cannot be reliable.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.